This invention relates to an image recording apparatus that is capable of recording images of high quality onto transmission originals with sufficient quantity of light even if they are overexposed negative originals.
Image recording apparatus such as color copiers and various types of color printers have chiefly been used to record images onto reflection-type originals such as printed matter. With the recent diversification in the art of recording image information, a new class of image recording apparatus have been commercialized that are capable of reading images not only from reflection-type originals such as printed matter and photographs but also from transmission-type originals such as negative films, slides, proofs and microfilms so that they are recorded onto light-sensitive and other image-receiving materials.
Image recording apparatus that can be used for both reflection and transmission-type originals are generally constructed in the following way: a light source unit that forms exposure optics for image recording from transmission-type originals is loaded onto the body of the recording apparatus and the light issuing from the light source in the unit is admitted through a transmission-type original, with the transmitted light being focused to form an image on a light-sensitive material (or a screen or a photosensor), thereby exposing it.
In this dual type of image recording apparatus, ordinary reflection-type originals are subjected to imagewise exposure with the exposure optics in the body of the recording apparatus which is a combination of a scanning head that extends one-dimensionally for issuing light of illumination, a plurality of mirrors, light modifying color filters and diaphragm, an imaging lens, etc.
To perform imagewise exposure with the exposure optics in the body of the image recording apparatus (which is hereunder referred to as the "exposure optics in the body"), the scanning head is moved in a scanning direction generally perpendicular to the direction in which it extends, whereby the reflection-type original on the document platen is scanned two-dimensionally with the light of illumination. The reflected light in the form of a slit coming from the reflection-type original is reflected by the plurality of mirrors to travel in predetermined optical paths, adjusted not only in color and the quantity (intensity) of light by means of the color filters and the diaphragm but also in the position of image formation, magnification, etc. by the imaging lens, and is admitted to form an image on the light-sensitive material for exposure in a predetermined position of imagewise exposure as it is transported in synchronism with the movement of the scanning head.
For recording images from comparatively large transmission-type originals such as slides and contact print strips with the 4.times.5 size, it is known to use a light source unit for that particular purpose which is adapted to illuminate a transmission-type original from above as it is placed on (or held near to) the document platen in the body of the image recording apparatus.
To read from transmission-type originals using this light source unit, one may utilize the aforementioned exposure optics in the body; stated more specifically, the light issuing from the light source unit and that has passed through the transmission-type original is scanned without lighting the light source in the scanning head, whereby the transmitted light from that original is similarly focused on the light-sensitive material to form an image in the position of imagewise exposure so that said light-sensitive material is exposed in accordance with the image of the transmission-type original.
For recording images from small-size transmission-type originals such as negative films of 135 or Brownie (120) size and slides of comparable size, Unexamined Published Japanese Patent Application (kokai) Hei 2-242246 has disclosed a film scanning unit having exposure optics of a projection type.
This type of film scanning unit is used as it is loaded onto a predetermined area of the body of an image recording apparatus and it has various components such as a projecting light source, light modifying color filters, an ND filter for adjusting the quantity of light, a document holder for holding and transporting (scanning) the transmission-type original, a slit for regulating the light passing through the transmission-type original, a zoom lens as an imaging lens and a mirror for adjusting the optical path.
An image recording apparatus using the above-described film scanning unit is shown conceptually in FIG. 9. The image recording apparatus generally indicated by 100 in FIG. 9 comprises essentially a light source 102, a light adjusting member 104, a diffuser plate 106, an aperture 108 having a slit 108a that extends longitudinally into the paper, a zoom lens (or imaging lens) 110, a reflector 112, and means (not shown) for transporting a transmission-type original G.
For recording the image of the transmission-type original G with the illustrated apparatus 100, the light issuing from the light source 102 is reflected by the reflector 112 composed of elliptical mirrors 112a and 112b and a circular mirror 112c and thereafter travels toward the original G. The reflector 112 is so designed that it has a focal point on the diffuser plate 106 in registry with the optical axis L of the imaging lens.
The light reflected by the reflector 112 is subsequently adjusted in color balance and the quantity (intensity) of light by means of the light adjusting member 104 composed of three color filters (C, M and Y) before it is launched into and diffused by the diffuser plate 106.
The light diffused by the diffuser plate 106 is launched into the transmission-type original G carried on a document holder (not shown) and the resulting transmitted light carrying the image of the original G then passes through the slit 108a in the aperture 108 to become elongated slit light.
The transmission-type original G (hence the document holder) is transported in a document scanning direction indicated by arrow a which correspond to the direction of the movement of the light-sensitive material A in the body of the recording apparatus. Since the slit 108a extends longitudinally into the paper (in a direction generally perpendicular to the direction of transport), the result will be the same as if the original G were subjected to slit scanning.
The transmitted light which has passed through the slit 108a then passes through the imaging lens 110, whereby it is enlarged to a magnification setting before it is launched into the exposure optics in the body. In the exposure optics in the body, the optical path of the transmitted light is brought into alignment with that of the aforementioned reflected light from the reflection-type original by means of a mirror that can be inserted into or removed from the optical path of the transmitted light; thus, as in the recording of the image of the reflection-type original, the transmitted light is launched into and focused to form an image on the light-sensitive material A being transported in synchronism with the transport of the transmission-type original G, hereby exposing the light-sensitive material A.
In the above-described image recording apparatus 100 depending on slit scanning for exposure, the light that has been diffused by the diffuser plate 106 and which has passed through the transmission-type original G will contribute to the exposure of the light-sensitive material A but this is due to the portion of the transmitted light that has passed through the slit 108a in the aperture 108 to be incident on the entrance pupil of the imaging lens 110.
The aperture 108 serves to restrict the image range so as to reduce possible deterioration in resolution (due to lens distortion) during scanning and, hence, it is essential to the purpose of accomplishing the recording of high-quality image. The diffuser plate 106 will produce the diffused light that is necessary to render less noticeable dust, flaws and other defects that have built up or occurred on the transmission type original G and this is also indispensable to the purpose of accomplishing the recording of high-quality image.
In fact, however, the need for the diffuser plate 106 and the aperture 108 has lowered the efficiency of utilization of the light from the light source 102 in the conventional model of image recording apparatus 100, making it sometimes impossible to insure an adequate amount of exposing light.
Stated more specifically with reference to FIG. 9 in which rays of light from the light source 102 are shown to be spaced apart by equal angles, the light travelling directly from the light source 102 toward the diffuser plate 106 is divergent whereas only the rays that are convergent on the diffuser plate 106 are those of the light that has been reflected by the elliptical mirrors 112a and 112b and which are launched into the diffuser plate at angles; hence, the proportion of the diffused light that will pass through the aperture 108 linearly to be incident on the entrance pupil of the imaging lens 110 is low enough to reduce the efficiency of utilization of light.
Additionally, in order to enhance the resolution of the image being recorded, the slit 108a formed in the aperture 108 has to be narrow but then the effective viewing angle of the imaging lens 110 will become even narrower to further reduce the efficiency of utilization of light.
Compared to those to be recorded on positive films such as reversal films, the images to be recorded on negative films have wide density ranges and image recording apparatus that are capable of using negative films as transmission-type original G must occasionally handle those negative films which have images recorded at inappropriately high density (as overexposed). However, as mentioned above, the conventional model of image recording apparatus 100 permits only inefficient utilization of light, so if the image of transmission-type original G to be recorded has been overexposed, a sufficient quantity (intensity) of the transmitted light to expose the light-sensitive material A cannot be launched to the entrance pupil of the imaging lens 110 so as to expose the light-sensitive material with a sufficient amount of exposing light, thereby making it impossible to achieve the recording of high-quality image.
With a view to insuring a sufficient amount of light for exposing the light-sensitive material A, one may think of increasing the quantity of light available from the light source 102, adjusting optical members such as imaging lens 110 or extending the time of exposure. However, adjustments by the light source 102 or the imaging lens, particularly a zoom lens, as an optical member are limited in effectiveness whereas extending the exposure time has the disadvantage of taking much time for image recording.